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Commit ebe0bbf0 authored by Harald Welte's avatar Harald Welte Committed by David S. Miller
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[NETFILTER] nfnetlink: use highest bit of nfa_type to indicate nested TLV 



As Henrik Nordstrom pointed out, all our efforts with "split endian" (i.e.
host byte order tags, net byte order values) are useless, unless a parser
can determine whether an attribute is nested or not.

This patch steals the highest bit of nfattr.nfa_type to indicate whether
the data payload contains a nested nfattr (1) or not (0).

This will break userspace compatibility, but luckily no kernel with
nfnetlink was released so far.

Signed-off-by: default avatarHarald Welte <laforge@netfilter.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f40863ce

include/linux/netfilter/nfnetlink.h

+8 −4
Original line number Diff line number Diff line
@@ -41,11 +41,15 @@ enum nfnetlink_groups { 
struct nfattr

{

	u_int16_t nfa_len;

	u_int16_t nfa_type;

	u_int16_t nfa_type;	/* we use 15 bits for the type, and the highest

				 * bit to indicate whether the payload is nested */

} __attribute__ ((packed));



/* FIXME: Shamelessly copy and pasted from rtnetlink.h, it's time

 * 	  to put this in a generic file */

/* FIXME: Apart from NFNL_NFA_NESTED shamelessly copy and pasted from

 * rtnetlink.h, it's time to put this in a generic file */



#define NFNL_NFA_NEST	0x8000

#define NFA_TYPE(attr) 	((attr)->nfa_type & 0x7fff)



#define NFA_ALIGNTO     4

#define NFA_ALIGN(len)	(((len) + NFA_ALIGNTO - 1) & ~(NFA_ALIGNTO - 1))
@@ -59,7 +63,7 @@ struct nfattr 
#define NFA_PAYLOAD(nfa) ((int)((nfa)->nfa_len) - NFA_LENGTH(0))

#define NFA_NEST(skb, type) \

({	struct nfattr *__start = (struct nfattr *) (skb)->tail; \

	NFA_PUT(skb, type, 0, NULL); \

	NFA_PUT(skb, (NFNL_NFA_NEST | type), 0, NULL); \

	__start;  })

#define NFA_NEST_END(skb, start) \

({      (start)->nfa_len = ((skb)->tail - (unsigned char *) (start)); \

net/netfilter/nfnetlink.c

+2 −2
Original line number Diff line number Diff line
@@ -133,7 +133,7 @@ int nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len) 
	memset(tb, 0, sizeof(struct nfattr *) * maxattr);



	while (NFA_OK(nfa, len)) {

		unsigned flavor = nfa->nfa_type;

		unsigned flavor = NFA_TYPE(nfa);

		if (flavor && flavor <= maxattr)

			tb[flavor-1] = nfa;

		nfa = NFA_NEXT(nfa, len);
@@ -177,7 +177,7 @@ nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys, 
		int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);



		while (NFA_OK(attr, attrlen)) {

			unsigned flavor = attr->nfa_type;

			unsigned flavor = NFA_TYPE(attr);

			if (flavor) {

				if (flavor > attr_count)

					return -EINVAL;